[Development] A new approach for Qt main()

Bogdan Vatra bogdan.vatra at kdab.com
Fri Dec 9 14:19:27 CET 2016

On vineri, 9 decembrie 2016 12:58:46 EET Eskil Abrahamsen Blomfeldt wrote:
> Den 09.12.2016 12:40, skrev Tor Arne Vestbø:
> > On 09/12/2016 11:44, Lars Knoll wrote:
> >> Well, the problem is that the main() entry point is causing huge amounts
> >> of issues on at least Android and iOS.
> > 
> > I don't know about Android, but on iOS this is patently false. While
> > the workaround is complex, it has worked very well in the 3 years
> > since its inception. Please don't use iOS as a straw-man in this
> > discussion.
> Speaking for Android, there are and have been thread synchronization
> issues due to Qt running a synchronous event loop in the main function.
> It is also impossible to make applications with multiple entry points
> and complex life cycles, which you would expect in an Android
> application consisting of several activities and services that can be
> triggered independently and simultaenously. Our work-around for this is
> to limit support to applications with one activity or one service per
> process in the application.
> So while we have been able to find solutions for most our problems, both
> on Android and iOS, I guess Lars' point is that we are encountering more
> and more cases where we have to invent hacks and work-arounds and
> document limitations in order to be functional on modern platforms. It
> might be a sign that we should adapt.

IMHO (at least) for Android the biggest problem is the QPA architecture which 
is not designed for multiple Activities/Services. On Android we'll need a QPA 
instance for every Activities/Services :). This also means we'll need to 
redesign QtAndroidExtras as well.

Even if having  multiple Activities in the same process will be a nice thing, 
is not a very demanding feature. The most demanding feature will be to support 
multiple Services alongside an Activity in the same process.


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